This invention relates to a robot control system in which a predetermined task is executed by teaching a robot a position (hereafter referred to as "TCP") of a distal end of a working member (tool) mounted on a wrist of the robot.
When parts are assembled by using an industrial robot, it is necessary for prescribed parts to be repeatedly supplied to a set position at a predetermined timing by a parts feeder, which supplies the parts automatically. However, parts delivered in a flow by a conveyor belt, or the like, cannot always be accurately supplied to the same position every time. Accordingly, an offset for the TCP that has already been taught for the hand must be corrected by reading, via a TV camera, or the like, position information relating to the part to be manipulated, and feeding the information into the robot each time.
In such cases, in accordance with the prior art, an amount of rotational correction obtained from a sensor such as a camera is calculated in terms of displacement of the a rotational angle with regard to three basic axes of a hand vector. The tool offset at a taught position, serving as the origin of the correction, is corrected by a G45 preparatory code for a position rotating correction.
The position information sent to a robot from the sensor side is data indicative of an angle defined by a workpiece gripping direction vector, obtained by data processing on the sensor side, and a predetermined axis, e.g. the Xs axis, of the sensor coordinate system. Meanwhile, a robot calculation control unit stores the sensor coordinates upon converting them into data in the robot coordinate system. Consequently, when a rotational correction is performed which brings a unit vector (reference vector) in the direction of a predetermined axis, e.g., the Yt axis, of the tool coordinate system into coincidence with a gripping direction vector, of the workpiece, which of the Xt, Yt and Zt axes of the tool coordinate system the rotational correction will be performed about differs each time a workpiece is supplied. Moreover, control data, stored in the robot, regarding the sensor coordinate system, and control data in the tool coordinate system, for deciding the feedback data of the robot control unit, are both processed upon being converted into data indicative of the fundamental coordinate system of the robot. As a result, calculating the amount of rotational correction which brings the reference vector into coincidence with the gripping direction vector is very complicated.